Crystalline anhydrous amino tri(methylenephosphonic acid)

ABSTRACT

CRYSTALLINE ANHYDROUS AMINO TRI(METHYLENEPHOSPHONIC ACID) USEFUL AS A SEQUESTERING AGENT, A DEFLOCCULATING AGENT AND A DETERGENT BUILDER.

United States Patent ABSTRACT OF THE DISCLOSURE Crystalline anhydrous amino tri(methylenephosphonic acid) useful as a sequestering agent, a defiocculating agent and a detergent builder.

This is a continuation-in-part of application Ser. No. 152,048 filed Nov. 13, 1961 and now US. Pat. No. 3,288,846.

This invention pertains to a new and novel compound,

H crystalline anhydrous amino tri(methylenephosphonic acid).

K. A. Petrov and co-workers described the preparation of amino tri(methylencphosphonic acid) by the reaction of diethyl phosphite, ammonia and formaldehyde, followed by hydrolysis of the amino tri(rnethylenephosphonate) ester product to amino tri(methylenephosphonic acid) in Zhur. Obschei Khim., 29, 591-4 (1959) [Chem. Abs., vol. 54, 260 (1960)]. Amino tri(rnethylenephosphonic acid) was described in the foregoing article as a glassy mass. By following the teachings of Petrov et al., as described more fully hereinafter, amino tri(methylenephosphonic acid) prepared by the foregoing method was found to exhibit inferior physical and chemical properties which rendered it essentially unfit for any type of commercial use.

It has now been found that amino tri(methylenephosphonic acid), that is, a compound having the structure:

er and the like.

The following examples illustrate the present invention.

EXAMPLE I Into a conventional jacketed, glass-lined mixing vessel fitted with a water condenser are charged 246 parts of orthophosphorous acid, 53 parts of ammonium chloride, and 100 parts of water. The pH of the resulting mixture is about 0.5. This mixture is then heated to its reflux temperature, which under atmospheric pressure is about 108 C. Over a period of 30 minutes, while the mixture is being refluxed, a total of 95 parts of pa'raformaldehyde are 3,564,047 Patented Feb. 16, 1971 added slowly into the boiling mixture. After being refluxed for an additional 20 minutes, the mixture is cooled to ambient temperature and analyzed [by observing and measuring the nuclear magnetic resonance spectra (N.M.R.) of the product] to determine how much of the P-H bond (from HP0(OH) of orthophosphorous acid) has been converted to the N-C-P bond of the product, amino tri-(methylenephosphonic acid). By N.M.R. analysis, the product yield, based on the amount of phosphorous in the starting material, is about 95%. About 5% of the original orthophosphorous acid in the reaction mixture remains unreacted.

Upon cooling to about 20 C., crystalline anhydrous amino tri(methylenephosphonic acid) precipitates from the solution. By chemical analysis it is identified as practically pure amino tri(rnethylenephosphonic acid); found 12.3% C, 31.6% P, 3.92% H (calculated: 12.0% C, 31.1% P, 4.04% H). It exhibits the following X-ray diffraction pattern (CuK a radiation):

Line d,A.

a Five strongest lines in order of decreasing intensity.

EXAMPLE II The following is the preparation of amino tri(methylenephosphonic acid) by the foregoing described Petrov et al. method.

Into a conventional jacketed, glass-lined mixing vessel fitted with a water condenser are charged parts of 28% aqueous ammonia solution and 445 parts of diethyl phosphite. The mixture is cooled to -10 C. and 260 parts of 37% aqueous formaldehyde solution are added at a rate such that the temperature is maintained at 15 to 20 C. After addition, the reaction mixture is heated to reflux for about 1 hour. On cooling, the reaction product is neutralized to pH of 9 with 10% NaOH and extracted twice with equi-volume portions of benzene. The extract is then dried over K CO before distilling off the benzene and unreacted materials (diethyl phosphite) (150 C./ 10-15 mm. Hg). The product, hexaethyl amino tri- (methylenephosphonate) distills at 185.5-198 C. at 5x10 mm. Hg pressure with a yield of about 46 parts (10% by theory).

Six grams of the above prepared ester are then placed in a glass tube with 40 cc. HCl (1:1), sealed and heated at 140 C. for 5 hours. The contents of the tube, after being opened, are poured into a flask and placed on a steam bath. The HCl is removed by alternately evaporating to dryness (aspirator vacuum) and dissolving in water. At the end of two days and after using 1,000 ml. of water, the HCl was still present in the product. Titration with base indicates the product, a dark brown glass, contains about amino tri(methylenephosphonic acid).

The following table sets forth a comparison of the physical and cherriical properties of the crystalline anhydrous amino tri'(methylenephosphonic acid) of the present invention (Example I), and amino tri(methylenephosphonic acid) prepared by the Petrov et a1. method (Example II).

TABLE 1 .lmino tri(rnethylene phos- Amino tri(methylene phosphonie Property phonic acid) Example I icid) Example II Physical appearance White. free-flowing crystals. Dark brown glass, amorphous. Hygroscopicity (24 hours at 60% RH, 25 C.) A .15% wt. gain, still ireedlowing Over 3% wt. gain, turns soupy (very lnonhygroseoplc) hygroscopic). Melting point J10-2l2 C.(d) oftens -90 C. Rateif dissolution in water (0.7 grams in 100 cc. H O at 1'07 V32.

25 Active concentration on product by titration. i00% l. About Sequestration of Ca (grams of Ca by grams of ma- 13.6 About 8.8.

terial at pI-I-ll in presence of 0.1% NazCzOl. I I Ease of purification Obtalged as pure, crystalline Could not be purified by l'eprecipitapro uct. tion. Ease of milling May be ground to powder..... Impossible to handle in mill, tends to gum up.

1 When this material was dissolved in Wa ter and ace tone added to effect precipitation, the product separated out as a dark, viscous oily layer.

As can be appreciated from the foregoing table. the References Cited crystalline anhydrous amino tri(methylenephosphonic UNITED STATES PATENTS acid) exhibits superior physical and chemical properties 328 358 8/1943 Pitman as compared to the amino tri(methylenephosphonic acid), 5 7/1958 Berswo'rth an amorphous glassy mass, prepared by the Petrov et al. 2/1966 Bani method and the compound of the present invention is 3,288,486 11/1966 Iraniet 1 suitable for commercial use while the compound prepared by the Petrov et a1. method, as drammatically illustrated from the foregoing, is essentially unsuitable for commercial use. As can be appreciated from the foregoing, the compound of the instant invention is truly a compound OTHER REFERENCES Petrov et al., Chem. Abst.," vol. 4, col. 260 (l960). Kosolapoff, Organophosphorus Compounds" 1950), pp. 143, and 156.

of a different kind than the compound represented by BERNARD HELFIN, p i Examiner the Petrov et al. method.

What is claimed is:

" l. E. EVANS, Assistant Examiner l. Crystalline anhydrous amino tri(methylene phos- U.S.Cl.X.R. 

